The long-term objective of this proposal is to investigate the hypothalamic control of gonadotropin release in the non-human primate, as a model for the human. The hypothalamic peptide, luteininzing hormone- releasing hormone (LHRH), is released in a pulsatile manner and controls ovarian function through pituitary gonadotropin. Estrogen from the ovary, in turn, feeds back to give a signal regulating pulsatile LHRH release. Abnormalities in the pulsatility of gonadotropin release and estrogen secretion are associated with several reproductive disorders. The goal of this application, therefore, is to investigate the cellular mechanism of LHRH pulse generation and the mechanism of estrogen action using primate LHRH neurons. Two specific aims are proposed. The first aim will test the hypothesis that LHRH neurosecretion occurs as a consequence of synchronized neuronal activity. Cultured primary LHRH neurons derived from the embryonic olfactory placode of rhesus monkeys will be used. Activity of LHRH neurons will be assessed by electrophysiological approaches, by monitoring intracellular calcium signaling, and by measuring LHRH neurosecretion from individual LHRH neurons. The second aim will examine the cellular mechanisms of estrogen action in LHRH neurons. We will examine 1) the effects of estrogen on electrical firing activity, intracellular calcium signaling, and LHRH neurosecretion, 2) the ability of estrogen to modify the responsiveness of LHRH neurons to gamma aminobutyric acid (GABA) and test 3) a novel hypothesis that the BK potassium channel mediates estrogen action. Results from the. proposed project will provide insight into the mechanisms through which the hypothalamus controls gonadotropin release in primates and ultimately will be useful for clinical management and the control of fertility.